This is a major about-face for Microsoft. A decade ago, Steve Ballmer called Linux "a cancer" thanks to its open source license. Microsoft has tried threatening Linux companies and Linux users. It has also successfully gone after companies that make devices based on Linux (or derivatives like Android) threatening them with patent lawsuits unless they pay it per-device fees.

But Microsoft's battle to bully companies into giving up Linux didn't work and Linux grew into a popular choice in the data center and in the cloud.

By adding Linux as an option, Microsoft's cloud has become more of a head-to-head competitor with Amazon AWS infrastructure-as-a-service cloud.

This doesn't mean that Linux lovers will flock to Microsoft Azure. They'll continue to stick it out with Amazon, and other more popular clouds for Linux like Linode.

But it's a very good sign for Microsoft and its future in cloud computing. Windows lovers don't have to go elsewhere if they to use a little Linux with their cloud providers (and they do).

Note that Azure won't support super arch rival Red Hat's version of Linux. It will only offer OpenSuse 12.01, CentOS 6.2 (a free open source knock off of Red Hat) and Canonical Ubuntu 12.04.